JayG

Was driving along, stopped at a traffic light and all of a sudden it started idling a little rough and the CEL started to flash and the computer said to drive slowly to service

Started to drive and after about 100 feet, the light went out and the engine was smooth again.

I was about 1 mile to my home, drove home and plugged in my durametric

There were 3 codes


This is the first time I have gotten ANY codes

I did a weekend at the track a week ago and all was good

I have 74k on the clock,. Plugs were changed at around 15k miles ago Just did an oil change before I went to the track. All the oil changes I have done since i bought the car a year ago have been good

Any thoughts????

5CHN3LL

Maybe the fuel pump is starting to act up - if it was bad gas or a clogged filter, I wouldn't expect it to stumble for a bit and then recover. Since it happened only at idle, a vacuum leak might be a possible suspect.

Sounds like you haven't driven it any more since you got home and read the codes?

5CHN3LL

Incidentally, it's "OH NO! THE DREADED CEL codes P300, P301, P303"

FRUNKenstein

Coils? Not sure why 2 would act up at once, but maybe they were already bad (cracked at the track) and something (hard bump) caused them to start showing symptoms simultaneously.

JayG

I drove it about an hour later for about 20 min and no codes and runs perfectly as before
some stop and go neighborhood driving, a good high speed run on the freeway and then some neighborhood driving.
maybe it was Sun Spots?

Gonzo911

Bad gas. Or mice.

ALE

Might be moisture and cracked coils.

gnat

I think you need the dreaded new stable of coil packs.

Need to get off my *** and do ours too (getting the 300 and 301).

JayG

Yea, could be the coil packs, but why would the CEL go out on its own after about 60 seconds?

gnat

If it is crack/water based it could be a transient short causing the misfire.

Kinda surprised the CEL went out though. I thought once it was triggered it stayed on (flashing accepted) until it was shutdown and restarted.

Macster

Because the error condition went away.

Flashing CEL denotes rich misfires and this suggests a malfunctioning injector. If this is what is going on it is probably confined to one injector. The misfires in the other cylinder could have been self-inflicted as the DME dialed back on the fuel and leaned out the other good cylinders to the point one of them then developed lean misfires.

When the bad injector recovered the DME of course resumed its normal fueling.

At 74K miles coils could be suspect but I think the engine would manifest misfires upon cold start in cooler more humid conditions. I have to point out while the coils of the engines of both of my cars cause misfires occasionally after an onset of damp cooler weather none of far have misfired at any time other than just seconds after a cold engine start.

JayG

If the problem is cracked coils and them getting wet, I suppose I could spray some water up that side of the engine when it is running and see if it throws a code

Is that a good idea?

As far as the injector, I did put a bottle of Techron about a month ago before I went to the track. I would think that would clean the injector, not plug it. Should I put another bottle in the tank?

The car also ran beautifully at the track and the drive to and from the track which was some great back road twisties up and down the mountain.

Should I check the fuel trims or ???

Macster

Spraying the water onto the engine/coils when the engine is running and warm is not likely to manifest any misfires unless the coils are pretty bad. If they were this bad they'd be misfiring without the need to wet them.

Even though my Turbo misfires upon cold start once in a while when dampness comes in the only odd behavior the engine manifests when I start it after a washing is the belt slips from the water. The engine doesn't misfire.

Techron can loosen deposits in the fuel system and it could have been a flake, a tiny particle that got caught in the injector momentarily before being pulverized and flushed out.

Generally injectors are protected from this by fine screen so the particle would have to have been loosened from downstream of the screen, somewhere in the relatively small volume of the injector body that is between the screen and the tip/nozzle.

It doesn't have to be a particle though. The injector is an electro-mechanical device and it could have suffered a momentary problem that caused it to not close completely or to for some reason react less quickly to the removal of power and thus extend the active time the time injector was open.

If the latter it will likely do this again as the failure mode becomes less intermittent and more constant.

There is another failure mode and that is an injector failed to open fully, and the DME added fuel to compensate and this triggered rich misfires from one of the two healthy cylinders.

The sick injector recovered and of course the DME resumed normal fueling and misfires ceased.

Regardless, I don't think -- at least this would be my opinion were the situation reversed -- I don't think the above is sufficient to warrant replacement of the injectors, even just those on the "bad" bank.

For a more definitive diagnosis, maybe, would be to with a Porsche diagnostics computer connected to an up to temperature engine to disable each injector in turn and note teh RPM drop. The disabled injector that results in less RPM drop could be (could be) the "bad* one as that cylinder is contributing less than the other cylinders.

JayG

Can I do that with a durametric?

alpine003

That would be a good test. Generally I recommend peeps replace their coils while replacing plugs as most of these cars are 10+ years old and plastics will deteriorate from heat/age. You only need a micro-crack for codes to be thrown. When mine went bad, I couldn't even hardly see some of the cracks without breaking out the magnifying glass. Don't cheap out and replace all 6.